Coma and other altered states of awareness

In this post, I thought i shall talk about coma and other altered states of awareness. What do we mean when we say a patient is in coma? Just what does coma mean?

Coma has been defined differently in different medical and neurology textbooks. In simple terms it means a patient who has decreased conciousness to the extent he is not aware of his surroundings and does not respond when stimulated by the external means even when the stimulus is noxious or painful like a pinch applied to the skin of the nipple. These patients are usually seriously ill and are in the intensive care unit of the hospital. As they are unaware of their external surroundings they need to be supported, meaning that their diet has to be maintained, their fluid status, making sure they are not constipated etc.

There can be numerous causes for coma. some of them are related to the brain itself and some of them are systemic, that is they affect the body.

1) Neurotrauma: head injuries frequently can lead to a coma with loss of consciousness sometimes for prolonged periods of time. Intracranial hemorrhage or bleeding into the brain is one cause of this. This bleeding raises the intracranial pressure and this compresses the brainstem and hence leads to coma.

2) Large stroke: a large stroke can lead to loss of consciousness and coma. Again a large stroke frequently leads to an increase in intracranial pressure and this leads to a depression in the state of awareness and coma.

3) Infections of the brain like meningitis and encephalitis may also lead to a state of coma.

4) Large tumors of the brain can also present with depression in sensorium (decreased consciousness) and coma.

5) Frequent seizures one after the other (this condition is referred to as status epilepticus): patients may be unresponsive even though they are not visibly  “shaking” (that is there are no convulsive movements but patients are unresponsive because their brain is still having seizures).

6) Anoxic hypoxic injuries to the brain: anoxia is lack of blood flow and oxygen to the brain. This kind of coma is frequently irreversible.

7) Systemic causes of coma: metabolic conditions like low sodium (hyponatremia), low blood glucose (hypoglycemia), metabolic acidosis ( as seen in diabetic ketoacidosis), liver dysfunction (cirrhosis), renal dysfunction and renal failure, congestive heart failure, hypercapnia (where there is too much carbon dioxide in the blood) all are common causes of coma.

8) Toxins: ingestion of toxins like drugs of abuse, heavy metals, insecticides, overdose of antidepressants, pain killers, sedatives can all lead to coma.

 

As the causes of coma are protean, when patients present to the hospital in a comatosed state, we do a rapid triage and try to localize the etiology of the coma. Blood is drawn to check for sodium, potassium, liver and renal functions and glucose. If there is some evidence that an infectious etiology is the cause of coma we may draw blood for culture and do a spinal tap to examine the spinal fluid to rule out meningitis. Depending upon the history and examination findings other investigations may be carried out like CT scan brain, MRI brain, Chest X-ray, EEG and so on.

The treatment of “coma” depends upon the cause of coma. Frequently as I stated above these patients need to be admitted to the intensive care unit and need respiratory and circulatory support. Depending upon the cause of the coma, they may or may not need neurosurgical intervention. If there is a big bleed in the brain and the intracranial pressure is too high, the blood may need to be removed (evacuated). These patients may need broad spectrum antibiotic coverage if they have an infection or an antiepileptic drug if they are having seizures. If toxin or drug ingestion is the cause, then we try to remove the toxin or drug from the blood stream with the aid of an antidote.

Nitin Sethi, MD

MRI white matter lesions: does it represent MS?

MRI white matter lesions

Many times I get consulted by patients or their relatives when their MRI brain report reads multiple scattered white matter lesions seen. The radiologist’s report usually further reads that these can be seen in primary demyelinating conditions like multiple sclerosis or in vascular disorders. Patient’s and caregivers are naturally worried when they get this MRI report and do not know what to do and how to proceed further. So I thought that here I shall talk about these white matter abnormalities seen on the MRI. What is their significance? Do they represent evidence of multiple sclerosis?

White matter signal changes on the MRI essentially means that on the MRI, the white matter  showed some scattered bright spots. White matter in the brain refers to the fiber tracts that carry information to and fro from the brain.

My first question when somebody asks me what next and what does this mean is to ask them why was the MRI done in the first place. If the MRI was done because there was a clinical suspicion of multiple sclerosis then these white matter lesions may indeed have significance and may represent radiological evidence of MS plaques. Let me explain this with an example. You go to your doctor, you have signs and symptoms that suggest MS (example you may have had an attack of optic neuritis), when the doctor examines you he is able to elict signs in the examination compatible with a diagnosis of MS, then he orders an MRI to see if you do have evidence of white matter lesions in the brain. In a case like this the presence of white matter lesions/ signal changes in the MRI is obviously important. Here it likely does suggest the presence of MS. That said and done I again want to re-emphasize that the diagnosis of MS is made on the basis of clinical history of previous attacks, CSF (spinal fluid) examination and MRI, not just on the basis of the MRI alone. Also there are certain criteria which have to be satisfied on MRI to make a definite diagnosis of MS. These radiological criteria for MS include the number of lesions on  the MRI, their location and their size.

Thus it is important to remember that a person who is noted to have white matter lesions on a brain MRI does not necessarily have MS. White matter lesions can be seen in numerous other conditions and they are more commonly seen as we grow older. The thinking behind this is that they represent microvascular ischemic changes in the brain (the smaller caliber blood vessels in the brain showing signs of ischemia or decreased blood flow). Hence these white matter abnormalities on MRI are more commonly seen in patients who have microvascular and macrovascular risk factors such as a history of hypertension, diabetes and high cholesterol (dyslipidemia/ bad lipid profile).

White matter signal changes on MRI may also be seen in patients who have infectious and other inflammatory conditions. They have been reported in the MRI of patients with a history of migraine headaches (migraine too is a vascular disorder and that may explain the connection).

So I want to end by saying that the presence of these white matter signal changes on brain MRI has to be correlated to the history, clinical examination and other ancillary investigations. Your doctor shall help you in going about this in a methodical manner. I repeat these white matter lesions do not suggest MS in each and every case they are found.

 Dr. Sethi

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